The use of light-emitting proteins for the detection of biomolecules provides fast and sensitive methods which overcome the disadvantages of radioactive labels and the high cost of fluorescent dyes. This reference work summarizes modern advanced techniques and their applications and includes practical examples of assays based on photoproteins. The book presents contemporary key topics like luminescent marine organisms, DNA probes, reporter gene assays and photoproteins, ratiometric sensing, use of photoproteins for in vivo functional imaging and luminescent proteins in binding assays, to name just a few, and is complemented by recent advances in instrumentation.